Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy below 100 eV: probing first-row transition-metalM-edges in chemical complexes

X-ray absorption and scattering spectroscopies involving the 3dtransition-metalK- andL-edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using theM-edges, which are below 100 eV. Synchrotron-based X-ray sources can have higher energy resolution atM-edges.M-edge X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) could therefore provide complementary information toK- andL-edge spectroscopies. In this study,M2,3-edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition,M2,3-edge RIXS on NiO, NiF2and two other covalent complexes have been performed and differentd–dtransition patterns have been observed. Although still preliminary, this work on 3dmetal complexes demonstrates the potential to useM-edge XAS and RIXS on more complicated 3dmetal complexes in the future. The potential for using high-sensitivity and high-resolution superconducting tunnel junction X-ray detectors below 100 eV is also illustrated and discussed.